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[Python-Dev] Tuning Python dicts

Antoine Pitrou solipsis at pitrou.net
Sat Apr 10 22:40:26 CEST 2010 
Reid Kleckner <rnk <at> mit.edu> writes:
> 
> I think you're right about the number of collisions, though.  CPython
> dicts use a pretty low load factor (2/3) to keep collision counts
> down.  One of the major benefits cited in the paper is the ability to
> maintain performance in the face of higher load factors, so I may be
> able to bump up the load factor to save memory.  This would increase
> collisions, but then that wouldn't matter, because resolving them
> would only require looking within two consecutive cache lines.

Why wouldn't it matter? Hash collisions still involve more CPU work, even though
if you're not access memory a lot.


Antoine.
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